Hi I am using Ubuntu and have successfully installed WinXP in VirtualBox (first time using it, great bit of kit). The only issue is I created a 2GB disk and now its full. I did set it to dynamic size but it has not expanded, so what should I do? Is there a way to manually expand it? I could not find anything in the manual or poking around in the disk manager.

Chamstar, I am in the same boat... sort of. I am running Ubuntu Feisty Fawn and Virtual Box windows xp on a fixed 5 GB hdd size. I would like to enlarge the size by 3 GB. I would realy hate to do all of the xp updates again!

I thought I would have the answer by now, maybe you cannot resize disks?
I would find this a bit strange, and I don't know if to file my problem as a bug since I actually have a dynamic disk and its not re-sizing... There is plenty of room on the real disk for a file increase.

dynamic disk are in fact disk with specified size (eg.: 2GB) which are not fully allocated when created, so it could have size of 15 KB (just an example), then you'll format it and add a 500 KB file, size become now 584 KB (always an example), and so on until it reach it's max size: 2GB. It is not a disk which will grows and grows as needed !

There is 2 options: the most reliable is to create a bigger disk and copy content from the first to this one (with something like backup tool), the other one is a bit tricky, you'll have to modify the geometry of virtual disk and resize partition with a partition tool like parted on Linux.
I succeed with 2nd solution with a WinXP system disk (I was bored to use 1st solution ), I have twice the size now, but the inside size of vdi is still the older. It's work, no error at all.
To do this I have just write a little patch for vditool. I'll send it soon to dev.

Thanks and you prob. think I'm a bit daft but I still cannot get it to work, tried downloading with ff and wget and I just get 'command not found' when I try vditool from the command line, I can see it when I do ls (its on my Desktop).

If I type vdi then hit tab it does not autocomplete, I get vdir instead!! Sorry I know this is hardly related to the issue of resizing a vdi...